ISRO (Indian Space Research Organization) developed HySIS, a full-fledged hyperspectral EO (Earth Observation) satellite for launch in 2018. The HySIS is meant to provide hyperspectral imaging services to the country for a range of applications in agriculture, forestry and assessment of coastal zones, inland waters, soil and other geological environments, etc.

HySIS, the primary satellite of PSLV-C43 mission, weighing about 380 kg, is an Earth observation satellite configured around ISRO's Mini Satellite-2 (IMS-2) bus. The primary goal of HysIS is to study the Earth's surface in the visible, near infrared and shortwave infrared regions of the electromagnetic spectrum.

Spacecraft

HySIS is a Hyper Spectral Imaging Satellite for providing global coverage on a repetitive basis to users and supplementing the data from the existing multispectral sensors. A wide range of applications in agriculture, forestry, geological environments, coastal zones and inland waters , etc. are derived from the satellite data.

Figure 1: Photo of the HYSIS satellite (image credit: ISRO)

Built around the IMS-2 (ISRO Mini Satellite-2) bus, HySIS is 2.158 m x 1.386 m x 1.121 m with a mass of 380 kg. The satellite's payload also consists of a 730 W power backup, and a 64 Ah Li-ion battery. The mission design life of HySIS is 5 years.

Figure 2: Photo of the HySIS minisatellite (top) along with the secondary (passenger) payloads during encapsulation (image credit: ISRO)

Launch: The HySIS minisatellite was launched on 29 November 2018 (04:28 UTC, 9:58 IST) on a PSLV-C43 vehicle from SDSC (Satish Dhawan Space Center) SHAR on the east coast of India. 1)

The co-passengers of HysIS include 1 microsatellite and 29 nanosatellites from eight different countries (23 are from the USA) . All these satellites have been commercially contracted for launch through ISRO's commercial arm Antrix Corporation Limited. The total mass of the secondary payloads is 261.5 kg. 3)

• Two Lemur-2 nanosatellites (5 kg each) of Spire Global. Both satellites were developed under ESA's ARTES program to prove the value of nanosatellites in weather monitoring (spaceborne radio occultation). Experts can use these measurements to glean temperature, pressure and humidity information for weather forecasting and climate change monitoring. Named ‘Space as a Service', the Spire Pioneer mission intends to prove that nanosat GNSS-RO is a commercially-viable alternative to traditional methods. ESA's Pioneer initiative partners with companies like Spire to help them provide this kind of in-orbit demonstration and validation for third parties. 4) The two tiny satellites will collect and distribute GNSS-RO data during their commissioning phase, after which they will go into full commercial data production mode, gathering weather information for meteorological institutions, maritime and aviation customers on demand.

• In addition two more Lemur-2 3U CubeSats of Spire Global with HQs in San Francisco were onboard.

• Centauri I nanosatellite of Fleet Space Technologies, Australia. Centauri I is a 3U nanosatellite, designed by Fleet Space Technologies and built by Pumpkin Space Systems.

• CICERO-8 (Community Initiative for Cellular Earth Remove Observation-8) is a 6U CubeSat of GeoOptics Inc., Pasadena, CA. The nanosatellite carries a radio occultation payload that will use signals from both GPS and European Galileo satellites.

• HSAT-1 of Harris Corporation is another 6U, CubeSat. HSAT-1 will carry out a technology demonstration mission and carries Earth imaging and AIS receiver payloads. HSAT-1 will use Globalstar satellites for its primary method of communication with the ground, with an S-band radio carried as a backup. The satellite is expected to operate for two years.

• Hiber-1 is a 6U CubeSat of Hiber Global of the Netherlands. Hiber-1 is a demonstration mission for a future planned low Earth orbit communications network. Hiber plans to launch up to fifty satellites to provide worldwide connections for IoT (Internet of Things) devices.

• CASE – which is being carried for Canada's Kepler Communications – will serve as a pathfinder for a constellation of communications satellites to link IoT devices. Named after a robot in the film Interstellar, CASE follows on from the KIPP satellite that was deployed by a Chinese Chang Zheng 11 rocket in January. CASE is a 3U CubeSat that was built by Glasgow-based Clyde Space.

• FACSAT-1, the first 3U CubeSat to be operated by the Colombian Air Force, the Fuerza Aérea Colombiana (FAC). Built by Sweden's GOMSpace, FACSAT-1 is primarily a demonstration mission, although it carries an imaging payload that will be used for agriculture and land use monitoring, disaster response and urban planning in Colombia. The satellite can image the Earth at resolutions of up to 30 m.

• InnoSat-2 (Innovative Satellite-2), a 3U CubeSat to perform a series of technology development experiments for Astronautic Technology (M) Sdn. Bhd. (ATSB), Malaysia.

• Reaktor Hello World is a 2U CubeSat built by Finland's Reaktor Space Lab. The objective is to demonstrate an amateur radio beacon and a hyperspectral imaging payload.

• 3Cat-1 is a 1U CubeSat of the Polytechnic University of Catalonia, Barcelona, Spain [also known as UPC (Universitat Politècnica de Catalunya)], to test a suite of instruments and equipment in space. It will test CellSat solar cells designed for future missions, a micro-electromechanical sensor to detect atomic oxygen, a graphene field-effect transistor (GFET), a wireless power transfer system and an autonomous beacon transmitter powered by a Peltier cell – independent of the rest of the satellite's systems – that will continually broadcast the satellite's temperature. For calibration, 3Cat-1 is also equipped with a Geiger counter and a low-resolution camera.

• The largest of the secondary payloads was Global 1, the first member of an Earth-imaging constellation being deployed by American company BlackSky Global of Seattle, WA, USA. Global-1 carries a SpaceView-24 imaging system developed by Exelis which uses a 24 cm telescope to image the Earth's surface at resolutions of up to 90 cm. The 56 kg Global-1 microsatellite was constructed by Spaceflight Services, based around the SCOUT bus, and is designed to operate for at least three years. BlackSky plans to deploy a constellation of up to sixty satellites.

Figure 7: First light image of HySIS acquired on 2 December 2018 showing Lakhpat, a sparsely populated town in the Indian state of Gujarat. The town is enclosed by 7 km long 18th-century fort walls (image credit: ISRO/NRSC)

Sensor complement: HysIS (Hyperspectral Imaging System)

HysIS carries two payloads — One to capture images in the VNIR (Visible Near Infrared) range of the light spectrum and another in the SWIR (Shortwave Infrared, 0.85-2.4 µm). The instrument uses the pushbroom technique featuring 55 spectral bands in VNIR (0.4-0.95 µm) with bandwidths of 10 nm and a spatial sampling of 30 m from a 636 km orbit. 6)

The optical imaging detector array chip in the satellite has been designed by ISRO's Ahmedabad-based SAC (Space Application Center) and manufactured by its SCL (Semi Conductor Limited), an autonomous body under the Department of Space in Chandigarh.

The chip architecture (Figure 8), device design,chip layout, and package design were carried out at SAC to meet project requirements with respect to spatial and temporal resolution, dynamic range, MTF (Modulation Transfer Function), smear and spectral responsivity. 1000 x 66 pixels were designed to be readout, from both top and bottom directions, using four analog video ports to meet the frame rate requirement. Metal strapping was used for swiftly transferring integrated charges from image to storage region, in order to reduce image smear. Designs (both at chip and package levels) went through detailed review, before clearing for mask making and package fabrication, by a team consisting of members from SCL and SAC.

Wafer processing was completed at SCL with top priority. During wafer processing at SCL, the SAC team developed a test bench (hardware, firmware, and software for providing electro-optical stimuli) for electrooptical evaluation of the chip. Wafer level testing, assembly and packaging were carried out at SCL. Few dies were packaged (chip-on-board) at SCL for functionality verification.

The COB (Chip on Board) packages have successfully gone through functional verification checks at SAC. Figures 9, 10 and 11 are images of COB, test setup electronics, and EO test bench, respectively. Raw images generated under normal laboratory illumination conditions at F#2, a focal length of 105mm, and an integration time of 30 milliseconds and acquired by the chip, are given in Figures 12 and 13.

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (herb.kramer@gmx.net).